Anesthetist{3 s ventilator

ABSTRACT

An anaesthetist&#39;&#39;s ventilator in the form of a valve comprising a body having a gas inlet connection for connecting to anesthetic equipment, a breathing connection for enabling a patient to breathe through the valve and an outlet to atmosphere, a valve member, and biassing means biassing the valve member to a fixed rest position in the body wherein it closes the gas inlet connection and opens the breathing connection to the outlet, the valve member being adapted, upon buildup of pressure at the gas inlet connection momentarily to be displaced against the action of the biassing means to open the breathing connection to the gas inlet connection and at least partially close the outlet, and then, as a result of consequential lowering of the pressure at the gas inlet connection, and increase in pressure in the breathing connection to return to its rest position.

United States Patent [72] Inventor Edwar Ca l 3,473,529 /1969 Wallacel/65X Stockport, Cheshire, England (Cavendish 2,667,895 2/1954 251/65House, Pries'tnall Road, l-leaton Mersey) 2,807,421 9/1957 251/360 [2 1]Appl- N 700,668 3,063,461 11/1962 137/102 1 Filed J -8,1968 3,068,85612/1962 128/1455 P n e F b. 1971 3,449,970 6/1969 Klatt 74/89 PrimaryExaminer-William F. ODea 5 AN Assistant Examiner-David J. 0 Claims 2 i gFigs. Attorney-Kenwood R058 [52] U.S.Cl 137/102,

128/ l 88; 251/65,}51/213 ABSTRACT: An anaesthetists ventilator in theform of a 6 m 17/00 valve comprising a body having a gas inletconnection for con- 128/188, necting to anaesthetic equipment, abreathing connection for 142, 185, 186; 137/102, 256, 588, 1 12, 458,enabling a patient to breathe through the valve and an outlet 505.11;251/65, 630; 74/69, 89.15, 107, 89, 99, to atmosphere, a valve member,and biassing means biassing 3, 1 the valve member to a fixed restposition in the body wherein it closes the as inlet connection and 0 usthe breathin con- [56] Refe'enm c'ted nection to th e outlet, the valvememb f being adapted, upon ITE STATES PATENTS buildup of pressure at thegas inlet connection momentarily to 2,811,979 11/1957 Presnell 25 l/X bedisp a d against the action of the biassing means to p 3,203,439 3/1965B k 251 /65X the breathing connection to the gas inlet connection and at3,265,062 8/ 1966 Hesse 251/65X least partially close the outlet, andthen, as a result of con- 3,27(),763 9/1966 Kief r 251/65X sequentiallowering of the pressure at the: gas inlet connection, 3,279,487 10/1966Elam 251/65X and increase in pressure in the breathing connection, to3,351,092 1 1/1967 lngerfield et a1 251/65X return to its rest position.

ANAESTIIETISTS VENTILATOR This invention concerns an anaesthetistsventilator, that is to say a device enablingthe respiratory system of apatient (e.g. a paralyzed anaesthetised patient) to be ventilated, i.e.connected alternately to source of gases under pressure for inspirationand to atmospheric air for expiration.

An object of the invention is to provide a construction of ventilator asaforesaid which can conveniently be employed in conjunction withconventional anesthetic apparatus, which can be manufacturedcomparatively inexpensively so as to be readily portable, and which issimple and efficient in operation.

With these objects in view, the present invention provides ananaesthetists ventilator in the form of a valve comprising a body havinga gas inlet connection for connecting to anesthetic equipment, abreathing connection for enabling a patient to breathe through the valveand an outlet to atmosphere, a valve member, and biassing means biassingthe valve member to a fixed rest position in the body wherein it closesthe gas inlet connection and opens the breathing conmotion to theoutlet, the valve member being adapted, upon buildup of pressure at thegas inlet connection, momentarily to be displaced against the action ofthe biassing means to open the breathing connection to the gas inletconnection and at least partially toclose the outlet, and then, as aresult of consequential lowering of the pressure at the gas inletconnection and increasing of the pressure in the breathing connection,to return to its rest position.

The biassing means may conveniently comprise one or more permanentmagnets.

The valve body may conveniently be in the form of a T- member, thecrossbar of the T providing respectively the gas inlet connection andthe outlet at its two ends, the leg of the T providing the breathingconnection. I

The valve may conveniently comprise a spool-type valve member axiallymovable in the crossbar of the T and adapted to cooperate, by its ends,with seats provided by annular shoulders provided in said crossbar.

In some circumstances, it is desirable for the period and/or extend ofopening of the breathing connection to the gas inlet to be adjustable orvariable, and this may be achieved by providing for variation of thepossible extend of movement of the valve member, e. g. by making theposition of the valve seat of the outlet variable. a

In a first preferred embodiment of the invention, there are two magnets,one of which serves as an attracting magnet which acts to attract thevalve member'into and tends to retain it in the rest position, and theother of which serves as a repulsion magnet acting to repel the valvemember from its position closing the outlet and tending to return it toits rest position.

In a second embodiment, only ,a single magnet, preferably an attractingmagnet, is provided. a

It may be desirable to provide, in the outlet, a supplementary nonretumvalve serving to prevent atmospheric air entering the valve body throughsuch outlet;

In order that the invention may be fully understood, it will bedescribed further, by way of example, with reference to the accompanyingdrawings which illustrate two practical embodiment of the ventilator ofthe invention, it being understood that the following details areillustrative and not limitative of the scope of the invention. In thedrawings:

FIG. 1 is a cross-sectional side elevation of a first embodi-' ment ofthe ventilator of the invention; and

FIG. 2 is a view similar to FIG. 1, but showing a second embodiment.

As can be appreciated from FIG. 1, which illustrates a simple embodimentof the ventilator, such ventilator effectively being in the form of anautomatically-actuated double-acting valve.

This valve comprises a body made of a suitable nonmagnetic metal (suchas aluminum alloy) or of a tough plastics material and composed of threeparts namely a main T-piece 11 and two extension pieces 12 and 13respectively. The T- piece 11 is generally of conventional appearance,and comprises a hollow crossbar l4 and a hollow leg part 15, the latterconnecting with the crossbar 14 substantially midway. along the lengthof the crossbar 14. The leg part 15 is of slightly tapered form, havingits smallest diameter at its free end so that a flexible tube (notshown) leading to an endotracheal tube or an anaesthetist's face mask(not shown) may be fitted thereto. The leg part 15 of the T-piece llaccordingly constitutes a breathing connection of the valve body,enabling a patient to breathe through the valve.

Each end of the crossbar 14 of the T-piece ll is internally threaded andhas screwed therein a respective one of the extension pieces 12 and 13referred to above. Each such extension piece 12 and 13 comprises asleeve l6, 17 respectively merging at one end with a respective slightlyenlarged externally-threaded spigot part l8, 19 which screws into therespective end of the crossbar 14 of the T-piece 1]. Each of suchsleeves l6, l7 merges with the respective spigot part l8, 19 to provide,within the body, a respective abrupt annular shoulder 20, 21, these twoshoulders 20, 21 facing each other along the crossbar 14 of the T-piece11 and each constituting a respective seat of the valve.

Internal circumferentially spaced ribs 20a and 21a respectively areprovided within the spigot parts 18 and 19.

The extension piece 12 constitutes an outlet of the valve, and is formedwith an internal diametrically disposed fixed web 22. This has aninternally threaded hole approximately through its midpoint, this holeaccommodating a rodlike outlet magnet 23 which is externally threaded toengage in the hole and extend axially of the respective extension piece12. Within the valve body, the outlet magnet 23 terminatesin aslightly-tapered end 24 at a position short of the shoulder or seat 20in the outlet 12; at the other end the outlet magnet 23 projects out ofthe outlet 12 and terminates in a knurled knob 25, whereby adjustment ofthe disposition of the inner end 24 of the outlet magnet 23 relativetothe plane of the seat 20 can be efiected.

The other extension piece 13 constitutes a gas inlet connection of thevalve and accommodates a diametrically-disposed adjustable web 26 havinga respective rodlike gas inlet magnet 27 extending therethrough,substantially along the axis of the crossbarl4 of the T1 T-piece 11. Theadjustable web 26 has curved feet 28, 29 at its radially-outward endsfor lying snugly against the inner curved surface of the gas inletconnection 13, and the foot 28 has a slot therealong 30 extending partof the way parallel to the axis of the gas inlet connection. 13. A grubscrew 31 set into the gas inlet connection 13 engages in the slot 30 toprevent the web 26 rotating relative to the gas inlet connection 13whilst at'the same time permitting movement of the web 26 along the gasinlet connection 13. Since the slot 30 does not extend along the wholelength of the foot 28, the web 26 is held captive by the screw 31 and islimited in its possible movement towards the open end of the gas inletconnection 13 by abutment of the screw against the end of the slot 30.An adjusting screw 32 extending radially through the gas inletconnection 13 about halfway along the sleeve 17, and having a knurledknob 33 on its outer end, engages an inclined surface on the adjustableweb 26, so that screwing-in of the adjusting screw 32 serves to displacethe adjustable web 26 and its magnet 27 away from the main T-piece 11,and unscrewing of the screw 32 permits displacement of the web 26 andmagnet 27 towards the Tpiece 11, for adjustment of inner end 35 of thegas inlet magnet 27 relative to the seat 21. The magnet 27 is adjustablyretained in the web 26 by the respective grub screws 36.

A spool valve member 37, in the fonn of a tubular hub 38 having disclikeflanges 39 and 40 at each end, is accommodated in the crossbar 14 of'the T-piece 11. The length of the valve member 37 is such that theflanges 39, 40 thereof are disposed one in each of the spigot parts 18,19 of the extension pieces 12, 13 and are centralized by the respectiveribs 20a and 21a0 whilst being readily slidable thereon, but the spacingbetween such flanges 39, 40 is shorter than the axial distance betweenthe two seats 20, 21 of the valve so that the valve member 37 can engageone only of the seats 20, 21 by one of its flanges 39, 40 at any time.The flanges 39, 40 are a clearance fit in the respective spigots 18, 19,and the flange 39 in the outlet 12 of the valve is slightly smaller thanthe flange 40 which is in the gas inlet connection 13 of the valve.

Set into each end of the hub 38 of the valve member 37 is a respectiverod-like magnet 41, 42 respectively, these being axially disposed andprojecting respectively towards the outlet magnet 23 and the gas inletmagnet 27, and being retained by respective grub screws 43, 44 wherebythe extend by which they project from the respective ends of the hub 38is adjustable. The magnet 42 which faces the gas inlet magnet 27constitutes a spool retaining magnet and the magnet 41 which faces theoutlet magnet 23 constitutes a spool return magnet. The arrangement issuch that like poles of the outlet magnet 23 and the spool return magnet41 confront one another and tend to displace the spool valve member 37towards a rest position wherein the disc of flange 40, which ischamfered as indicated at 45, engages with the seat 21 in the gas inletconnection 13. Further, the gas inlet magnet 27 and the spool retainingmagnet 42 has have opposite poles confronting one another, so that thesemagnets 27 and 42 attract one another and act to tend to retain thespool valve member 37 in its rest position aforesaid.

in operation of this embodiment of the ventilator, the breathingconnection 15 will have an appropriate tube (not shown) connectedthereto, this leading either to a face mask (not shown) applied over apatient's nose and/or mouth, or more usually to an endotracheal tube(not shown) appropriately fitted to the patient, and the gas inletconnection 13 will have connected thereto a respective flexible tube(not shown) leading to conventional anesthetic apparatus (not shown) forsupplying gases under pressure, such apparatus including an inflatablebladder.

With the valve member 37 in the rest position, above described, whereinthe flange 40 abuts the seat 21, gases issuing from the anestheticapparatus initially build up the pressure in the inflatable bladder andin the flexible tube to the gas inlet connection 13, passage of thegases to the breathing connection 15 being prevented by the largediameter flange 40 of the spool valve member 37 abutting the seat 21 inthe gas inlet connection 13, and the combined efforts of the gas inletmagnet 27 and the retaining magnet 42 serving to resist separation ofsuch large diameter flange 40 from such seat 21.

As soon as the pressure in the gas inlet connection 13 is sufficient toovercome the force of the gas inlet magnet 27 and the retaining magnet42, the spool valve member 37 is forced away from the seat 21 in the gasinlet connection 13 and the gases from the anesthetic apparatus can passthrough the valve by way of the gas inlet connection 13 and thebreathing connection 15 to the patient, so as to inflate the patientslungs. The movement of the spool valve member 37 is an impulse movementand is such that the smaller diameter flange 39 thereof moves towardsthe seat in the outlet 12, tending momentarily to-close the latter,although actual closure may not occur in practice since the returnmagnet 41 and the outlet magnet 23 tend to repel one another and havethe effect of impulsing the spool valve member 37 back to its initialrest position whilst the patient is expiring spent air from his lungsthrough the breathing connection 15 and the outlet 12. Return of thespool valve member 37 to its rest position is possible, because of theopening of the gas inlet connection 13 to the breathing connection 15causes a drop in the pressure in the inflatable bladder and the flexibletube to the gas inlet connection 13, permitting the large diameterflange 40 of the spool valve member 37 to move back into engagement withits seat 21.

Accordingly, so long as gases under pressure are supplied to the gasinlet connection 13, the valve member 37 will be periodically impulsedto open the gas inlet connection 13 to the breathing connection 15 forinflating the patients lungs and the valve member 37 will automaticallyreturn to its rest position permitting the patient to expire through thebreathing connection 15 and the outlet 12.

Adjustment of the screw 32 by way of its knob 33 serves to' shift thegas inlet magnet away from or closer to the retaining magnet 42 andthereby vary the force with which the valve member 37 is biassed towardsits rest position. This adjustment accordingly serves to determine thebuildup of pressure necessary in the inlet connection 13 before thevalve member 37 will be impulsed. correspondingly, adjustment of theoutlet magnet 23 relative to the spool return magnet 41 serves todetermine the actual stroke of movement of the spool valve member 37 andthe force with which such member 37 will be returned toward its restposition.

ln practice the ventilator above described is found to operateparticularly reliably and, of course, it is of simple constructionhaving only one effective moving part.

Referring now to F IG. 2, the embodiment here illustrated is of moreadvanced design than that just described, but is again in the form of anautomatically-actuated double-acting valve.

This valve again comprises a body made of a suitable nonmagnetic metal(such as aluminum alloy) or of a tough plastics material and composed ofthree parts namely a main T-piece 50 and two extension pieces 51 and 52.The T-piece 50 is generally of conventional appearance, and comprises ahollow crossbar 53 and a hollow leg part 54, the latter connecting withthe crossbar53 substantially mid way along the length of the crossbar53. The leg part 54 is of slightly tapered form, having its smallestdiameter at its free end so that a flexible tube (not shown) leading toan endotracheal tube or an anaesthetist's face mask may be fittedthereto. The leg part 54 of the T-piece 50 accordingly constitutes abreathing connection of the valve body, enabling a patient to breaththrough the valve.

Each end of the crossbar 53 of the T-piece 50 is internally threaded andhas screwed therein a respective one of the extension pieces 51,52referred to above. Each such extension piece comprises a sleeve 55,56merging at one end with a respective slightly enlargedextemally-threaded spigot part 57,58 which screws into the respectiveend of the crossbar 53 of the T-piece 50. Each sleeve 55,56 merges withthe respective spigot part 57,58 to provide, within the body, arespective abrupt annular shoulder 59,60, the two shoulders 59,60 facingeach other along the crossbar 55 of the T-piece 50. In this case, incontrast to the embodiment of FIG. 1, the shoulders 59,50 do not provideseats of the valve.

The extension piece 51 constitutes an outlet of the valve.Telescopically arranged in, and a close sliding fit in such an outlet 51is a tubular outlet seat member 61 the innermost end of which ischamfored to constitute a seat 62 of the valve which projects past theadjacent shoulder 59 and a short distance into the crossbar 53 of theT-piece 50. Adjustment of the extent by which the seat 62 projects pastthe shoulder 59 is provided for by a radial adjusting screw 63 engagedinto a threaded hole in the seat member 61 and extending through aslightly angled slot 64 in the outlet 51, the screw 63 carrying a collar65 locating in the slot 64 and having an enlarged head 66 whereby it maybe loosened or tightened manually. Accordingly, when the screw 63 isreleased, movement of the screw 63 and collar 65 along the slot 64 willcause the seat 62 to project into the crossbar 53 to a greater or lesserextent, the seat member 61 being subject, of course, to slightrotational movement within the outlet 51 during the adjustment.

The extension piece 52 is somewhat longer than the outlet 51 andconstitutes a gas inlet connection of the valve, accommodating anadjustable guide plug 67, of a tough plastics material, having arod-like gas inlet magnet 68 extending therethrough, substantially alongthe axis of the crossbar 53 of the T-piece 50, a grub screw (not shown)serving adjustably to locate the magnet 68 in a fixed position relativeto the plug 67.

The guide plug 67 is externally generally of cylindrical configurationto fit snugly within the interior of the gas inlet connection 52. At oneend a recess 69 is formed in the plug 67 for locating one end of a coilspring 70 the other end of which locates in an internal circumferentialgroove 71 in the gas inlet connection 52 near to the open end thereof.The spring 70 surrounds the gas inlet magnet 68. The other end 72 of theplug 67 is generally of frustoconical configuration, and gas passages 73are provided through-the plug 67.

"l" he outer curved surface of the ,plug '67 has a slot 74 therealongparallel to the axis of the gas inlet connection 52, and a grub screw 75set into the gas inlet connection 52 engages in the slot 74 to preventthe plug rotating within the gas inlet connection 52 whilst at the sametime permitting it to move along the gas inlet connection 52. Anadjusting peg 76 extends radially through the gas inlet connection 52near to its spigot 58, and has a knurled screw cap 77 on its outer endinthreaded engagement with a radial spigot 78. The peg 76 engages aninclined surface 79 on the plug 67, so that screwingin of the adjustingpeg 76 serves to displace the adjustable plug 67 and itsmagnet 68 awayfrom the main T-piece 50 and unscrewing of the peg 76 permits reversemovement of the plug 67 and magnet 68 towards the T-piece 50, under theaction of the spring 70, for adjustment of the inner end 80 of the gasinlet magnet 68 relative to the T-piece 50. The inclined surface 79 hasa steep portion 81 the purpose of which will be described later. a

The gas inlet connection 52 has a tubular valve housing 82 formed as anextension thereof. This housing 82 has one of its ends inwardly flangedas at83 to constitute a seat of the valve, such flanged end fittingintoand being secured into the spigot 58 of the gas inlet connection, sothat the housing extends into the crossbar 53 of the T-piece 50concentrically therewith. Slotted gas ports 84 are provided at intervalsaround the housing 82 adjacent the flange 83.

A spool valve member 85, in the form of a tubular hub 86 having disclikeflanges 87 and 88 at each end, is accommodated in the housing 82. Thelength of the valve member 85 is such that it can engage only one of theseats 62 and 83 by one of its discs or flanges 87 or 88 at any time,even when the outlet seat member 61 is adjusted to project to thegreatest possible extent towards the seat 83. The flanges 87,88 are, ofcourse, a free sliding fit in the housing 82.

Set into one end of the hub 86 of the valve member 85 is a rodlike spoolmagnet 89, this being axially disposed and projecting towards the gasinlet magnet 68. The latter magnet 68 constitutes effectively a spoolattracting magnet. The arrangement is such that the gas inlet magnet 68and the spool magnet 89 have opposite poles confronting one another, sothat these magnets 68 and 89 attract one another and act to tend toretain the spool valve member 85 in arest position wherein itscorresponding disc or flange 88 engages with the seat 83 of the housing82 so as to close off the gas inlet connection.

A pressure relief 'valve 90 connects with the crossbar 53 of the T-piece50 at a position wherein it is always in communication with thebreathing connection 54 regardless of the position of the spool valvemember 85.

As shown, this relief valve 90 is a conventional Coxeter Heidbrink typevalve and comprises an internally-threaded boss 91 formed integrallywith or secured to the crossbar 53 so as to surround an aperture 92 insuch crossbar, perforations 93 being provided at intervals. around suchboss 91. A manually-rotatable valve screw 94 screws into'the boss 91,the extent by which it can be screwed in and out being restricted by agrub screw 95 extending through the boss 91 and engaging into acircumferential recess 96 around the screw 94. The screw has an axialbore 97 therethrough and a pin 98, having a valve disc 99 thereon,locates by one end in the bore 97. A spring 100 surrounding the pin 98is accommodated in a recess 101 in the lower end of the screw 94 andthis spring abuts by one end againstthe screw 94 and by the other endagainst the valve disc 99 to tend to hold the latter in a positionclosing off the aperture 92.

In operation of the ventilator, the breathing connection 54 will have aflexible tube (not shown) connected thereto, this leading either to aface mask applied over a patient's nose and/or mouth, or more usually toan endotracheal tube appropriately fitted to the patient, and the gasinlet connection 52 will have connected thereto a respective flexibletube (not shown) leading to conventional anesthetic apparatus forsupplying gases under pressure such apparatus including an inflatablebladder.

The adjusting peg 76 is adjusted, by means of the screw cap 77, to aposition wherein the spool attracting magnet 68 holds the spool valvemember in its rest position, as above referred to, with the disc orflange 88 abutting the seat 83. In this position of adjustment of thepeg 76, the latter contacts the inclined surface 79 of the plug 67 onthe steep portion 81 of such surface 79, so that fine adjustment of theposition of the spool attracting magnet 68 relative to the spool magnet89 is possible to provide corresponding fine adjustment of theattractive force between the magnets 68 and 89.

With the ventilator so adjusted gases issuing from the anestheticapparatus initially build up the pressure in the inflatable bladder andin the flexible tube to the gas inlet connection 52, passage of thegases to the breathing connection 54, being prevented by the flange 88of the spool valve member 86 abutting the seat 83 to close off the gasinlet connection 52, and the combined efiorts of the gas inlet magnet 68and the spool magnet 89 serving to resist separation of such flange 88from such seat 83.

As soon as the pressure in the gas inlet connection 52 is sufficient toovercome the force of the gas inlet magnet 68 and the. spool magnet 89,the spool valve member 85 is forced away from the seat 83 and the gasesfrom the anesthetic ap paratus can pass through the valve by way of thegas inlet connection 52, the ports 84 and the breathing connection 54 tothe patient, so as to inflate the patient's lungs. The movement of thespool valve member 85 is an impulse movement and is such that the flange87 thereof move'stowardsthe seat 62 of the outlet 51, tendingmomentarily to close the latter, although actual closure may not occurin practice, since the spool magnet 89 and the inlet magnet 68 tend tocontinue to attract one another and have the effect of impulsing thespool valve member 85 back to its initial rest position whilst thepatient is expiring spent air from his lungs through the breathingconnection 54 and the outlet 51. Return of the spool valve member 85 ispossible because the opening of the gas inlet connection 52 to thebreathing connection 54 causes a drop in the pressure in the inflatablebladder and the flexible tube to the gas inlet connection 52, permittingthe flange 88 of the spool valve member 85 to move back into engagementwith its seat 83, and it will be appreciated that telescopic adjustmentof theoutlet seat member 61 will serve effectively, to vary the possiblemovement of the spool valve member 85 and thereby vary the period and/orextent of opening of the breathing connection 54 to the gas inletconnection 5 2.

So long as gases under pressure are supplied to the gas inlet connection52, the valve member 85 will be periodically impulsed to open the gasinlet connection 52 to the breathing connection 54 for inflating thepatient's lungs and the valve member will automatically return to itsrest position permitting the patient to expire through the breathingconnection 54 and the outlet 55.

The pressure-relief valve serves, of course, to ensure that gas inletpressure cannot be reached in the breathing connection 54, (e.g. in theunlikely event of jamming of the spool valve member 85) and that anyexcessive buildup of pressure in the valve body can escape to atmosphereindependently of the outlet 55, the pressure at which relief will occurbeing adjustable, of course, by means of the screw 94.

With this construction of the ventilator, the spool valve member 85,can, by adjustment of the peg 76, be retained in its position, asillustrated in FIG. 2, closing the outlet 51 and keeping the breathingconnection 54 open to the gas inlet connection 52 so that, at the end ofan operation on a patient, the patient has to breathe out against thepressure of the gases in the gas inlet connection 52 through the reliefvalve 90. Thus, at the end of an operation, when it is desired tostimulate the patient into full reliance upon his own. respiratorysystem, the relief valve 90 is adjusted to open under a predeterminedpressure and then the adjusting peg 76 is adjusted to permit the s rin70 to move the as inlet magnet 68 into engagement" with the spool magnet89, to move the spool valve I member 85 into its position closing theseat 62 of the outlet 51 of the valve.

The breathing connection 54 is thereby opened permanently to the gasinlet connection 52, making it necessary for the patient, during hisbreathing, to expire against the gas pressure prevailing in the gasinlet connection 52, the relief valve 90 opening to permit escape of gasand/or expired air to the atmosphere when a predetermined pressure isexceeded in the gas inlet connection 52.

The invention is not confined to the precise details of the illustratedand above-described embodiments, and variations may be made thereto. Forinstance, in both instances, the ventilator may beformed with its outlet12 or embodying a nonretum valve arrangement preventing entry ofatmospheric air into the ventilator through the outlet 12 or 51. Thiscould be achieved by the provision of an apertured partition across theoutlet (the outlet 12 of the FIG. 1 embodiment being appropriatelymodified to allow for this) with a very lightlyloaded nonretum valvebeing provided to close the aperture in such partition.

It will be evident, of course, that instead of using magnet pairs, thatis to say the magnets 23 and 41, the magnets 27 and 42 and the magnet 68and 89, use could be made in each case of a single magnet and anassociated element of magnetic ma terial such as a soft iron rod.

Other modifications of the ventilator are, of course, possible. Forinstance, the valve member can be of a form other than a spool typemember, and the means biassing the same towards its rest position may beresilient means, e.g. a spring. If desired, rubber pads may be providedupon the confronting ends of the magnets to minimize metallic contactthereof during operation of the ventilator. Also rubber seatings can beprovided for the valve member to impinge upon to minimize noise.

Where a spool type member is employed in the ventilator, the dead space"in the valve body (i.e. the space therein occupied by gas or expiredair) can be minimized by making the hub of the spool as large a diameteras is practicable.

An inflatable bladder could be provided, connected directly onto the gasinlet connection, and the gas supply fed into the gas inlet connectionthrough a small side tube, to render the ventilator easily portable.

I claim:

1. An anaesthetist's lung ventilator communicating with anestheticequipment for connecting the respiratory system of a patient alternatelyto a source of gas under pressure for inspiration and to atmosphere forexpiration and comprising:

a valve body having a central bore communicating at one end with a gasinlet connecting to the anesthetic equipment for supplying the gas andat the opposite end with an outlet connecting to atmosphere andintennediate the gas inlet and outlet with a breathing inlet-outletconnecting to the patient;

an outlet seat telescopically and slidably mounted within the outlet andhaving an inner end facing the central bore and defining an outlet valveseat;

outlet seat adjustment means for selectively varying the extent ofprojection of the outlet seat into the central bore;

an adjustable apertured guide plug having an inclined surface and beingslidably mounted within the gas inlet;

a guide plug adjustment means extending through the gas inlet andengageable with the guide plug for displacing the guide plug toward andaway from the central bore;

a tubular valve housing fixed within the central bore and defining a gasinlet valve seat adjacent the gas inlet;

a spool valve reciprocable within the valve housing;

valve biasing means for biasing the spool valve to rest position andincluding a first magnet adjustably disposed in the gas inlet and asecond magnet carried by the spool valve and disposed for beingattracted by the first magnet;

and

all adapted and arranged upon the continuous supply of gas to the gasinlet for the successive and alternate shifting of the spool valvebetween non rest position adjacent the outlet valve seat for outletclosure assumed upon the buildup of pressure at the gas inlet andagainst the action of the valve biasing means for the patientsinspiration through the gas inlet and breathing inlet-outlet and restposition adjacent the gas inlet valve seat for gas inlet closure assumedupon the consequential lowering of pressure at the gas inlet andincrease of pressure at the breathing inlet-outlet for the patientsunrestrained expiration through the breathing inlet-outlet through theoutlet to atmosphere.

2. A ventilator as claimed in claim 1 wherein the first magnetcooperates with the second magnet carried by the spool valve to bias thelatter to the rest position.

3. A ventilator as claimed in claim I wherein the first magnet extendsthrough the guide plug adjustably arranged in the gas inlet.

4. A ventilator as claimed in claim 1 including a spring means whereinthe guide plug is spring loaded toward the spool valve.

5. A ventilator as claimed in claim 1 wherein adjustment of the guideplug is provided for by the guide plug adjustment means radially movablethrough the-gas inlet and abutting the inclined surface on the guideplug.

6. A ventilator as claimed in claim 5 wherein the inclined surfaceincludes a steep section providing for fine adjustment of the guide plugand first magnet relative to the spool valve in the rest position of thespool valve.

7. A ventilator as claimed in claim 1 wherein the guide plug can beadjusted to retain the spool valve in a position away from its restposition and closing the gas outlet.

8. A ventilator as claimed in claim 1 wherein an inwardlyflanged end ofthe valve housing fits into a spigot part of the gas inlet, the flangeproviding the gas inlet valve seat.

9. A ventilator as claimed in claim 1 wherein the outlet seat adjustmentmeans comprises a screw projecting radially from the outlet seat andthrough an inclined slot in the outlet.

10. A ventilator as claimed in claim 1 wherein a pressure-relief valveis provided on the valve body for communication with the breathingconnection.

1. An anaesthetist''s lung ventilator communicating with anestheticequipment for connecting the respiratory system of a patient alternatelyto a source of gas under pressure for inspiration and to atmosphere forexpiration and comprising: a valve body having a central borecommunicating at one end with a gas inlet connecting to the anestheticequipment for supplying the gas and at the opposite end with an outletconnecting to atmosphere and intermediate the gas inlet and outlet witha breathing inlet-outlet connecting to the patient; an outlet seattelescopically and slidably mounted within the outlet and having aninner end facing the central bore and defining an outlet valve seat;outlet seat adjustment means for selectively varying the extent ofprojection of the outlet seat into the central bore; an adjustableapertured guide plug having an inclined surface and being slidablymounted within the gas inlet; a guide plug adjustment means extendingthrough the gas inlet and engageable with the guide plug for displacingthe guide plug toward and away from the central bore; a tubular valvehousing fixed within the central bore and defining a gas inlet valveseat adjacent the gas inlet; a spool valve reciprocable within the valvehousing; valve biasing means for biasing the spool valve to restposition and including a first magnet adjustably disposed in the gasinlet and a second magnet carried by the spool valve and disposed forbeing attracted by the first magnet; and all adapted and arranged uponthe continuous supply of gas to the gas inlet for the successive andalternate shifting of the spool valve between non rest position adjacentthe outlet valve seat for outlet closure assumed upon the buildup ofpressure at the gas inlet and against the action of the valve biasingmeans for the patient''s inspiration through the gas inlet and breathinginlet-outlet and rest position adjacent the gas inlet valve seat for gasinlet closure assumed upon the consequential lowering of pressure at thegas inlet anD increase of pressure at the breathing inlet-outlet for thepatient''s unrestrained expiration through the breathing inlet-outletthrough the outlet to atmosphere.
 2. A ventilator as claimed in claim 1wherein the first magnet cooperates with the second magnet carried bythe spool valve to bias the latter to the rest position.
 3. A ventilatoras claimed in claim 1 wherein the first magnet extends through the guideplug adjustably arranged in the gas inlet.
 4. A ventilator as claimed inclaim 1 including a spring means wherein the guide plug is spring loadedtoward the spool valve.
 5. A ventilator as claimed in claim 1 whereinadjustment of the guide plug is provided for by the guide plugadjustment means radially movable through the gas inlet and abutting theinclined surface on the guide plug.
 6. A ventilator as claimed in claim5 wherein the inclined surface includes a steep section providing forfine adjustment of the guide plug and first magnet relative to the spoolvalve in the rest position of the spool valve.
 7. A ventilator asclaimed in claim 1 wherein the guide plug can be adjusted to retain thespool valve in a position away from its rest position and closing thegas outlet.
 8. A ventilator as claimed in claim 1 wherein aninwardly-flanged end of the valve housing fits into a spigot part of thegas inlet, the flange providing the gas inlet valve seat.
 9. Aventilator as claimed in claim 1 wherein the outlet seat adjustmentmeans comprises a screw projecting radially from the outlet seat andthrough an inclined slot in the outlet.
 10. A ventilator as claimed inclaim 1 wherein a pressure-relief valve is provided on the valve bodyfor communication with the breathing connection.